Mysterious Problem!

squawkVFR

New Member
Nov 5, 2014
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Hey guys!

New member here in a desperate need of help.
I am from Norway (living in Florida now) so please excuse my limited vocabulary.

Ive had my 08 GT 5speed with 120k miles for one year now.

The problem started one month after i got her(no warranty) I accelerated hard from stop, and in 3rd gear the car would start misfiring out of control. It went on with the same problem for a couple of days until i started running 93, which i have been using ever since. Problem solved.

However, this summer, it started again with terrible misfiring. But it is no longer at the top end of the rpm, but at idling and up to 2000. Past 2000rpm she is running good, although some days she lacks performance until reaching 3-4000rpm.

Let me try to explain. The problem is mostly, but not limited, to warm days with a engine driven for 20mins or more. It can be every time or just sometimes, but it appears to become more frequently the last months. Yesterday i couldn't even drive the darn thing because i needed to stay above 2000 all the time.

If i am driving around slow under 2000rpm in 1st, 2nd and sometimes 3rd she will start shaking out of control, making loud "clack-clack" noises and the rpm will drop down to 100-200, but the car never dies. The only way to make it stop is to rev it up to over 4000. After that she is running normal again and the rpm drops down to normal idling. Once i put her in gear and release the clutch it starts again. To prevent it from happen i need at least 2000 rpm to get her moving without this misfiring thing, but strangely she is okay if i have no gas at all. Problematic in small hills and such, but it starts once i hit the gas anyway.

She is also throwing code p0012 and p0340. The first one disappeared after i changed the sensor, and the second one comes and goes as it pleases.

I have tried changing:
Fuel filter
Oil and filter 2000 miles ago
Air filter
Spark plugs
Cleaned throttle body
Seafoam in tank and vacuum line
Alternator 5 months ago (read 13.7 today on idle with all lights on)
Camshaft position sensor A

I have no engine mods except catback.

Any help would be much appreciated. Please ask me if i need to explain better or clarify something.
 
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Thanks for the input. I took it to a experienced mustang mechanic and got a diagnosis. Turned out it was the cam phasers and one of the coils.

Thank you.
 
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